This invention relates to a process for preparing a cationic polymer. More particularly, it relates to a process for preparing a copolymer of a vinylpyridine and a vinylbenzyl quaternary ammonium salt in the form of a solution.
The preparation of cationic polymers by the polymerization of one or more ethylenically-unsaturated polymerizable cationic compounds has been known. The preparation of such polymers is described, for example, in Great Britain Pat. No. 807,488 (published Jan. 14, 1959) and in U.S. Pat. No. 4,190,717 (issued Feb. 26, 1980). In general, such polymers may be prepared by resort to bulk polymerization technique, by aqueous emulsion polymerization or by solution polymerization in a suitable organic solvent. The choice of a particular method of polymerization will frequently be dictated by the nature of the particular monomeric or comonomeric species desirably polyermized or by the physical or other properties required in the polymeric product to suit particular applications.
Cationic polymer materials have, for example, been utilized as mordanting materials in various photographic products and processes for the mordanting or fixing of dye image-forming materials. Typically, a mordant polymer will be desireably utilized in the form of a polymeric layer on a suitable substrate or support material and will be formed by coating the support with a coating composition containing the polymeric mordant material. Depending upon the particular polymerizable compound or compounds forming the polymeric mordant and the method utilized in the manufacture thereof, the polymeric mordant material may have certain disadvantageous properties. These properties may adversely affect coatability of the polymeric material. Thus, a polymeric material otherwise suited to application as a mordant material in photographic products or processes, may exhibit non-homogeneity or high viscosity. Additionally, precipitation of the polymer from a coating composition may adversely affect materials handling and coating of the polymeric material. Efforts directed toward the aqueous copolymerization of a vinylpyridine and certain ethylenically-unsaturated vinylbenzyl quaternary salts have been found to result in the production of a polymeric product of milk-like appearance and high viscosity. The tendency of the copolymeric product to undergo phase separation upon standing may also be observed. It will be appreciated that a process for the production of such copolymeric product in the form of a solution exhibiting characteristic homogeneity or uniformity will be especially advantageous from the standpoint of facilitating materials handling and measuring and the production of coatings of the polymeric material.